The AR-15 is the "Musket" of our age - an archetypal and indispensable implement for every American. (For every able-bodied American is a member of the Part II Militia, referred to in the Constitution.) The original Stoner invention of the AR-15 was first marketed for the Civilian Militia to equip themselves (as is the custom for Militia) in the early 1960s. Only later was the AR-15 adopted by the organized Militia (armed forces) as well.
It is perfectly within law for American citizens to make their own rifles and shotguns, without any assistance from government servants. It has been encouraged, in fact, from the very beginning of our country.
Here is a complete video guide for assembling your very own complete AR-15 from separate parts, building on a bare receiver and 'upper'. This will save a very significant amount of the cost of your AR-15, as well as give you the satisfaction and confidence. In doing so, you are also helping to assuage the current massive shortfall in timely manufacturing. As a side-benefit, it involves valuable skills and accomplishments you can help pass along to your children and neighbors.
If you cannot find or afford a receiver (the 'main' part of the rifle to build upon), perhaps you can make you own. See the link below -